#include <string.h>

char *strtok(char *restrict s, const char *restrict sep)
{
    static char *p;
    if (!s && !(s = p)) return NULL;
    s += strspn(s, sep);
    if (!*s) return p = 0;
    p = s + strcspn(s, sep);
    if (*p) *p++ = 0;
    else p = 0;
    return s;
}
